半干旱荒漠区柠条根际细菌群落结构与功能

Rhizosphere Bacterial Community Structure and Function of Caragana korshinskii in Semiarid Desert Area

本研究对宁夏荒漠区5个典型的柠条(Caragana korshinskii)群落根际土壤样品进行了16S rRNA和宏基因组高通量测序,分析了干旱荒漠生境下柠条根际细菌群落结构、氮循环基因多样性及其与环境因子的相关性。结果表明,柠条根际细菌分布于39个门,以放线菌门(22.69%~33.86%)和变形菌门(21.24%~31.79%)为主要优势菌门,其次是绿弯菌门(10.25%~16.39%)、酸杆菌门(11.09%~14.90%)、拟杆菌门(3.50%~6.67%)和芽单胞菌门(1.70%~6.43%)等;共有418个核心细菌属,各样品中都有不同数量的特有属,多样性极其丰富。宏基因组数据表明,柠条根际土壤中真细菌reads数占94.37%,其次为古细菌(5.35%)和真核生物(0.15%);最丰富的功能类别是氨基酸转运与代谢,其次是能量生产与转化,复制、重组和修复。与碳水化合物、氨基酸和能量代谢相关的功能基因最丰富,表明这些基因与各个生物类群的生长有着密不可分的关系。根际细菌参与氮代谢的相关路径主要包括异化性硝酸盐还原、同化性硝酸盐还原、反硝化、硝化以及固氮过程,其中异化性硝酸盐还原和同化性硝酸盐还原途径是氮循环的主要途径。相关性分析表明,土壤pH值、速效氮和全钾含量是影响柠条根际微生物组成的主要限制因子,有机质、总氮和有效磷含量显著影响氮循环功能基因丰度。

This study performed 16S rRNA and metagenomic high-throughput sequencing on rhizosphere soil samples of 5 typical Caragana korshinskii communities in the desert area of Ningxia.The bacterial community structure,nitrogen cycle gene diversity and their correlation with environmental factors were analyzed.The results showed that the rhizosphere bacteria of C.korshinskii were distributed in 39 phylum,with Actinobacteria(22.69%-33.86%)and Proteobacteria(21.24%-31.79%)as the main dominant phylum,followed by Chloroflexi(10.25%-16.39%),Acidobacteria(11.09%-14.90%),Bacteroidetes(3.50%-6.67%),and Gemmatimonadetes(1.70%-6.43%)etc..There were 418 core bacterial genus in all samples,and there were different numbers of special genus in each sample,the diversity was extremely rich.Metagenomic data showed that the number of Eubacterial reads in the rhizosphere soil of C.korshinskii accounted for 94.37%,followed by Archaea(5.35%)and Eukaryotes(0.15%).The most abundant functional category was amino acid transport and metabolism,followed by energy production and transformation,replication,recombination,and repair.Functional genes related to carbohydrates,amino acids and energy metabolism were the most abundant,indicating that these genes were closely related to the growth of various biological groups.The related pathways of rhizosphere bacteria involved in nitrogen metabolism mainly included dissimilation nitrate reduction,assimilation nitrate reduction,denitrification,nitrification and nitrogen fixation processes,among which both assimilatory and dissimilatory nitrate reduction pathways were the main pathways of the nitrogen cycle.Correlation analysis showed that soil pH,available nitrogen and total potassium content were the main determinators of the microbial composition of the rhizosphere of C.korshinskii.The content of organic matter,total nitrogen and available phosphorus significantly affect the abundance of nitrogen cycle functional genes.